Reducing extractor noise

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I am in the process of setting up a dust extraction system for my workshop. The vital bit is a cyclone, which discharges sawdust into a bin, hooked up to a vacuum cleaner which collects the dust. It's a pretty conventional setup. There are los of videos on u tube.

However, I bought a vacuum cleaner online. It's rated noise level was stated to be 48 dB. This seemed excellent, as most vacs are in the 70 to 80 range, and on a logarithmic scale, that's quite a difference.

However, as I should have known, if something seems to good to be true, it probably is.

When I fired it up, I didn't need sophisticated measuring devices to tell me it was way over 48.

So I am stuck with it and will try to incorporate it as originally intended and have started to look at sound attenuation.

The plan is to place the cyclone, vac and sawdust bin in a cabinet underneath a bench.

I am dealing with airborne noise as well as direct vibration.

Having done some research, it's not clear to me if it's mass, in the form of a sturdy cabinet, or special sound- deadening foam- as used in recording studios, that I need, or both.

If any members have experience of this, I would appreciate your advice.

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Put it outside mounted on a post or stand secured to the ground, not your shop, place it where you will have minimum bends on the suctions side, build a shelter around it with easy access for upkeep and cleaning. No point in taking up space inside, wiring with an inside switch should be easy and the hole for the suction pipe should not be a problem either, just use foam or rubber to seal, don't want hard contact with the structure. Enjoy your quiet and cleaner work space.

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Put it outside mounted on a post or stand secured to the ground, not your shop, place it where you will have minimum bends on the suctions side, build a shelter around it with easy access for upkeep and cleaning. No point in taking up space inside, wiring with an inside switch should be easy and the hole for the suction pipe should not be a problem either, just use foam or rubber to seal, don't want hard contact with the structure. Enjoy your quiet and cleaner work space.

Thanks jud, unfortunately I can't put it outside. I'm in a French town with 600 thick stone walls and fierce planning regs. As I said, I'm still not clear if it's mass or absorption or both that I need need to be really effective. If I put it in a brick box for example, as generators sometimes are, I'm sure that's more effective than a ply one, but recording studios use special profile foam, not just polystyrene.The answer is probably both. On, on

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Have seen walls made soundproof by double studding. Each side had it's own support 2 X 4 studding sitting on the same 2 X 6 sill. The studs were evenly spaced but alternating sides, so a sound absorbing curtain could be woven between them, when in place each side was finishing to match the rest of the structure, just 2" thicker than the 2 X 4 walls. Might be able to duplicate the effects of such a wall, using double boxes separated by, a curtain. The discharge air could be muffled by a series of furnace filters or filter material stacked inside a large tube made to fit your space and allowing a muffled depressurization your vacuum container inner box. Like most things, different ways to get the job done. Good Luck.

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As part of researching noise levels in my workshop, I came across noise- measuring apps online.Some of these are free. While they are not really the equivalent of professional noise- level meters, they are perfectly adequate for my purposes. My iPad now becomes my meter.

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Thanks Mark. As I said earlier, it's not clear to me if it is mass, in the form of a sturdy container, ( brick, plasterboard etc.), or absorption in the form of special foam , ( or some combination of both,) that will be most effective to reduce both airborne sound and direct vibration. Putting this kit in a foam- lined box of some sort will obviously lower noise levels, but as this will run for long periods, I'm keen to make it as efficient as possible. Seems to be a lot of conflicting info out there. Research continues.

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Absorptive material inside the box will be the key to sound deadening. One thing you might do is go here: https://sawmillcreek.org/forum.php. I use the laser forums a lot for info. The users are very helpful. You may have become a "user" and register. But a search on "dust extractor" should give you lots of hits.

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Absorptive material inside the box will be the key to sound deadening. One thing you might do is go here: https://sawmillcreek.org/forum.php. I use the laser forums a lot for info. The users are very helpful. You may have become a "user" and register. But a search on "dust extractor" should give you lots of hits.

Thanks for the Sawmill Creek connection. Very helpful.

As I said , reading noise reduction fora tells me the whole noise issue seems poorly understood, esp the relationship between mass and absorption. Research continues.

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I'm about to give up on general noise attenuation in the workshop as its going to be much simpler and cheaper to invest in some high-end ear protectors.

With some of my machines its almost impossible to economically reduce their noise output.

BTW if you are interested in the sound levels in your work area, take your own measurements. Values given by manufacturers are generally not the product of standardised testing, and are not tested while being used.

I am currently trying to source 65 mm dia. aluminium blast-gates and actuators. 100 mm seems to be the smallest I can find. I have used plastic ones before, but with mixed success. Any help would be much appreciated. Ball valves are also a possibility.

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Several years ago I built a sound reducing box for a compressor to be used at trade shows. I used the best rated sound absorbing rigid foam and batting I could find, but the main way sound escapes is through vents needed to feed air to the compressor (with a vacuum, the air has to get out) and other cracks. I ended up building a box with a double bottom so that the sound had to go through a bit of a zig-zag maze, somewhat like a Dorade vent. The double bottom also reduced the transmission of mechanical vibration. The maze was filled with batting, and the air inlet, made up of many small holes, faced the floor. Other than those holes, the box was sealed. Fortunately, for this application, the compressor didn't run often, so I didn't have to worry about heat from the compressor. Since a vacuum doesn't generate much heat, this shouldn't be a problem.

Avoid large, flat panels, unless they are very rigid. If it vibrates, it is basically a large surface to excite the air, just like the sound board of a guitar.

Use foam, especially egg-crate foam, or batting on the inside surfaces to absorb (damp) sound and avoid reflections off of hard surfaces. To some extent, a soft covering on the outside panels also helps to deaden sound. That's one of the reasons the inside of cars are carpeted or are covered with a hard foam (the other reason being to reduce injury in a crash).

As a last though, I wonder if putting a long hose on the air exit of the vacuum would help to contain the noise.

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Several years ago I built a sound reducing box for a compressor to be used at trade shows. I used the best rated sound absorbing rigid foam and batting I could find, but the main way sound escapes is through vents needed to feed air to the compressor (with a vacuum, the air has to get out) and other cracks. I ended up building a box with a double bottom so that the sound had to go through a bit of a zig-zag maze, somewhat like a Dorade vent. The double bottom also reduced the transmission of mechanical vibration. The maze was filled with batting, and the air inlet, made up of many small holes, faced the floor. Other than those holes, the box was sealed. Fortunately, for this application, the compressor didn't run often, so I didn't have to worry about heat from the compressor. Since a vacuum doesn't generate much heat, this shouldn't be a problem.

Avoid large, flat panels, unless they are very rigid. If it vibrates, it is basically a large surface to excite the air, just like the sound board of a guitar.

Use foam, especially egg-crate foam, or batting on the inside surfaces to absorb (damp) sound and avoid reflections off of hard surfaces. To some extent, a soft covering on the outside panels also helps to deaden sound. That's one of the reasons the inside of cars are carpeted or are covered with a hard foam (the other reason being to reduce injury in a crash).

As a last though, I wonder if putting a long hose on the air exit of the vacuum would help to contain the noise.

Thanks for your thoughts and practical suggestions. As I said in the post above, I'm giving up for the moment, and will address the problem later. I got a bit sidetracked with noise levels while designing a dust extraction system for my new work area- noise and dust being the two most important health considerations I want to sort out.

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